An electron of kinetic energy K collides elastically with a stationary hydrogen atom in the ground state. Then,

Options

A. `0 lt E lt oo`
B. `0 lt E lt 10.2 eV`
C. `0 lt E lt 13.6 eV`
D. `0 lt E lt 3.4 eV`

Answer

B

Explanation

For an elestic collision to take place, there must be less in the energy of electron . The hydrogen atom will absorb energy from the coliding electron only if it can get from ground state to first excited state, i.e. from `n = 1 to n = 2` state for this , hydrogen atom must absorb energy `E_(2) - E_(1) = - 3.4 - (- 13.6) = 10.2 eV`
So , if the electron posses energy less than `10.2 eV`, it would never lose it and hence collision would be elastic.